Semiautomatic telephone system



L. A. KILLE M 1,832,306

3 Sheets-Sheet 1 Filed April 50, 1930 SEMIAUTOMATIG TELEPHONE SYSTEM Nov. 17, 1931.

M/VE/VTOA LA/(ILLE we $71M ATTORNEY r Nov. 17, 1931. L. A. KILLE 1,832,306

SEMIAUTOMATIC TELEPHONE SYSTEM Filed April 30, 1930 v 3 Sheets-Sheet 2 lNVENTUFr L. A. K/LLE 'A T TORNEY Nov. 17, 1931. A. KlLLE' 1,832,306

SEMIAUTOMATIC TELEPHONE SYSTEM Filed April 30, 1930 3 Sheets-Sheet 5 A T TURNE Y BY 9165M i EllH! \gllHh Patented Nov. 17, 1931 i'rso rates F FE 1 LINDLEY A. KILLE, or BOONTQN, NEW ans-say, ASSIGNOR T BELL TELEPHONE LABO: RATOBIES, rnoonronaann, or nnw YORK,.N. Y., Acoaroaa'rmn on new YonK sEMI u'roMA'rre TELEPHONE sYs'rEM Applicationfilecl April 30,

This invention relates to semi-automatic telephone systems and more particularly-to a system for completing incoming calls to an unattended automatic satellite-oliiceat a dialing B switchboard position located in the terminating office to which thesatellite is connected by direct trunks. The object of the invention is the provision of means whereby a call coming from a distant oiiice for a in wanted subscriber in a satellite can be dialed directly from the B position and completed thereto by connecting the incoming trunk with the trunk outgoing to the satellite oiiice. Calls originating within the main office for 1.? the local satellite will be completed at the dialing A switchboard asat present.

More specifically, the invention contemplates the use of a preselecting trunking ar rangement at the B.position wherein the depression of a key designating the wanted satellite oiiice causes the assignment of a preselected trunk to the positionwhere the key is depressed, lights the associated trunk lamp.

thereat and connects the'position dial to the assigned trunk. With the dialing of the wanted subscribers number the connection is extended by automatic switches connected to the trunk at the satellite office. The operator completes the connection by inserting the plug-ended incoming trunk into the ack of the assigned trunk either before, during. or after dialing. When the operation of ,diah ing the number is completed and the two trunks are thus joined, a dial release key is operated which causes the dial to be disconnected from the trunk taken into use. 1 At the present time most automatic oifices are provided with dialing equipment only at the A switchboard positions for reaching wanted subscribers either within the exchange area, orto an unattended satellite oiiice. Where a call originates in a distant office and is routed through a second office,

' in order to reach a particular satellite connectcd with the said second office it is necessary to supply connecting trunks between the B and A switchboards thereat in. order to extend the incoming trunk to the A position which alone is provided with-dialing facilities for further cxtendingthe coneso. Serial No. 448,488,

, within the main oflice'itself.

1 In accordance with the-present invention,

one specific embodiment of which is disclosed herein by way of illustration, this is acc'om plished in the following improved manner: The trunks connecting the satellite with the main oifice are jack-ended at the B position and are multipled and terminate in. a similar manner at-each of the A positions.- Each Bpositi0n is provided with a rotary trunk selector for each satellite to be reached and the trunks appearing at the A and B positions are also multipled to the arcs of these selectors through a relay in the trunk which, when operated, closes the multipie to the B position equipment. The circuit of the rotary selector is arranged for the automatic preselection of a trunk so that, as soon-as a preselected trunk is seized at any position or is otherwise made busy, the selectors serving that trunk group in all positions are stepped oif the busy trunk and continue to rotate until" another idle trunk is found. Should all the trunks be busya circuit for stopping the selector is provided and a visual all trunks busy signal is given at each posi-' tion. This signal persists until onetrunk becomes idlewhereupon all theselectors are stepped to that idle trunk and remain there until it-isitaken into use.

A dial, a dial release key, a key individual toeach unattended satellite to bereached from the B position and a relay of association is provided thereat. The relay of associatiomtogether with inter-related circuits more particularly described hereinafter, serve to connect the dial with an assigned trunk after the depression of the satellite key.

When the operator receives a signal on an r trunk multipl ed thereat, but since the lamp,

circuit is under the control of the operated relay of association and since, also, when a trunkis taken up at one position it is made busy at all others, the lamp is caused to light only at the position where the trunk is taken into use. The operator dials the number in 1 theusual way and inserts the plug-ended calling trunk into the jack of the assigned,

trunk. The dial impulses are transmitted over the trunk through the wipers and wiper contacts of the selector and serve to step the automatic switches at the satellite office to the terminals of the wanted line. The dial release key is then depressed in order to disconnect the dial from the trunk. This key closes a circuit for stepping the selector 05 the trunk just used and the trunk is provided with an appropriate busy signal against interference either by the selectors at the B position, or by the operators at the/A position as more particularly described hereinafter. It is to be noted in this connection that no restriction is imposed upon the operator as to when the plug-ended incoming trunk is to be inserted into the outgoing trunk jack other than the fact that it v has to be inserted before depressing the dial release key. The trunk plug may be inserted into the jack either before, during, or after dialing.

The trunks which are thus used for extending connections to the satellite oifice are also multipled to the dialing A switchboard where they are available to the A operator for completing similar calls arising within the office itself. In this case, however, the trunks are not provided'with any preselecting equipment and therefore neither assignment lamps nor individual satellite keys are provided thereat. The operator makes a manualselection of a trunkby applying the ordinary sleeve test for a busy trunk and the dialing of the wanted sub scribe'rs number takes place after the A cord plug has been inserted into the outgoing trunk jack, the dial impulses inthis case being transmitted over the trunk through the tip and ring of the cord plug and tip and ring of the jack of the outgoing trunk. A trunk so taken into use by an A operator is, of course, made busy at the trunk selectors at the B positionscausing such selectors to Since be stepped off the busy trunk and on to an idle one.

The scope and purpose of the invention will be better understood by a consideration of the following detailed description taken in connection with the attached drawings in which Fig. 1-21 shows a regular A cord circuit and subscribers line at G, an inter-office trunk circuit at L, the outgoing trunk acli and B position dial and associated keys at D.

Fig. 1-13 shows a subscribers line, and dialing A cord at K and outgoing trunk jack at F. ,7

' Fig. 2 shows th'eoutgoing trunk circuit extending from the terminating office to the community dial oliice.

F ig- 3 shows the terminatin circuit.

Fig. 1 shows the manner in which the three drawing sheets should be arranged in order to disclose the invention completely.

The operation of the invention inconnection with an incoming call established over the interofiice trunk line shown at L in Fig. 1-A will now be described. It is to be understood that only such parts of the inter- 1 g trunltbetwcen the two ofiices and the assonated cord circuit will be'describcel as is necessary for a complete understanding of the invention both of these connecting circuits are well-known in the telephone art.

A call extended over the interoliice trunk shown at L in 1A by the A operator inserting the calling plug P of the ular A cord into the out 3 J of the interofiice trunk leadin to theterminating oilice. This operates relay 106 in the following circuit: Battery on winding 10 1 of the A cord repeating coil, winding of relay 105, lower contact of key 155, ring conductor 101. of calling plug 1 ring contact g 13 position 128 of outgoing trunk jack J, wi ding 107 of the interoftice trunk repeating coil, lower and upper windings in series of line relay 106, winding 108 of theinteroliice trunk repeating coil, tip contact 127 of outgoing trunk jack J, tip contact 133 of the calling cord;

top contacts of key 155, winding 103 of the 11" COIClIQQQZIiHIg' coil, to ground. Relay 106 causes the operation of relay 109 over a ators telephone circuit, thereby flashing lamp 111. as an indication to the B operator that a call is waiting on the trunk sociated with lamp 111.

Relays V The call is thenanswered by operatingkey 114' whlch, over its make contacts, operates relay; 115 over. a

circuit from battery on the bottom back. con-v tacts of relay 116, lower. winding. ofrelay 115, make contactsof key 11 1 to groundon con.- ductor 117 through the operators telephone circuit. hen key 114 is released,-relay 115 locks over a circuit from battery on the bottom back contacts of relay 116, upperjwinding. and top inner contacts,,norn1ally-made contacts of key 11 to the same ground on conductor 117. This locking ground is-also extended to the middle contact of the top inner contact combination ofrelay115'to conductor 118 of the operators telephone circuit. The operation of relay 115 connects the talking conductors 141 and 142 of the operators telephone circuit across the trunk talking conductors 143 and lettand thereby places the operators talkingv circuit across the trunk in the well-known manner. The

trunking operation. 'VVhen the B operator ascertains the number of thewanted subscriber and also the fact that this subscribers line terminates-in the community dial office, she depresses key 300 designating the wanted community dial office.- The operation of key 300 causes a circuit to be closed from ground on key 300 through both ofits contacts in series, conductor 330 lower winding of relay 301, selector brush 318 and-as-v sociated contact, conductor 322, winding-jot.

relay 216 to battery and, through the bottom contacts of this relay in parallel with low' resistance 2-27 to battery. Relay 301 is then energized in series with relay 216 ofthe; trunk and in parallel wlth resistance 227.;

However, due to the fact that the winding of relay 216 is,eat this time.. shunted by the low resistance 227 and due, also, to the fact that relay 301 is made fast to operate, relay 301 will operate and connect direct ground fromits top middle right contacts toconductor 322 before relay 216 can operate. ,Vhen direct ground is thus placed on conductor 322,

.-.; relay 216 operates. removing, at. its bottom contacts, resistance 227 from the parallel path to its winding. It also, removes a ground from its top contacts to conductor 323 and, on its front contacts, closes a circuiti over the bottom inner back contactsof relay 203 winding of relay 205 to battery, causing this relay to operate. The operation of relay 205 opens, at its top contacts, thetalking conductors 120 and 119 from'tho trunkjacks D at the dialing A positions'while, at it's bottominner front contacts. it establishes a-busy potential through resistance 223 to battery in parallel with resistance 222 to ground to the sleevev of these jacks, thus marking the trunk busy at all operators po-. sitions to which it is multipled. The back contact of the bottom inner contact com bination ofrelay 205 opens the circuit of relay 202. The effect of removing ground from conductor 323 when relay 216 operates will be considered hereinafter in the con-.

sideration of circuit conditions prevailing whenall trunks leading to the community dial office are busy.-

When relay 301 operates, it closes a circuit to energize its .own upper winding thru its topouter front contacts to ground on key 300,

byway of conductor 331, opens the path to relay 311 at its bottom contacts, connects ground to conductor 322as' already described, short-circuits its own lower winding with ground from its top inner right front con,

tacts, short-circuits relay 310 with battery at its top-inner left front contacts and operates relay 302 over a; circuit from battery at its top inner left front contacts, winding of relay 302, conductor 331 to ground on key 300. Re-.

lay 302 connects battery at its bottom inner I front contacts to the winding of relay 312 and also to conductor 31 1 byway of selector brush 320 and associated contact. It also closes the-trunk conductors 327 and 328 through to the position dial 315 by way of the two top outer front contacts of relay 302 and conductors 332 and 333 respectively. These two the community dial oflice by way of the top back contacts'of relay 218 where they connect with conductors 229 and 228 respectively.

The battery connected to conductor 314 closes a circuit to light lamp 334 which is associated with the multiple jack ofthe trunkin the switchboard of the position where key 300 was operated, indicating thereby to the operator thatthe trunk which is assigned for extending the call to the community dial office is ready to receive dial impulses.

' The ground connected to conductor 322 by the operation of relay 301 functions to clear conductors 326, 322, 327 and 328 of the trunk assigned to the Bioperators position under consideration from the selector brushes of other B position trunk selectors having access to the same dial community otfice over the same trunk group. The brushes of the trunk selector associated with the position" where dial key 300 has been operated remain connected to the associated contacts to which the conductors are wired. This is accomplished as follows:

The operation'of key 300, while depressed, in addition to operating relay 301 supplies, as well, a temporary locking ground for this relay onconductor 331 through the top outer front contacts'of the said relay toits upper 16o conductors, that is, 327 and 328, extend to winding as already described. 'Italso sup plies ranoperating ground for relay 302'as already described, which relay operates to a battery on the top inner left front contacts of relay 301 when this relay has operated. After key 300 has been depressed, but before relay 301 is operated, relay 311 is connectedto a momentary energizing circuit in series with the lower winding of relay 301 from- 312. Since, however, relay 301 is made fast to operate, 1t will open the operating circuit of relay 311 at its bottom back contacts before relay'311 can operate sufficiently to close h its front contactf' The trunk selector 329 remains positioned, therefore, on the trunk assigned since its circuit is completed through the contacts of relay 311. l-

- It was stated hereinbefore that the trunk selectors associatedwith all positions are-of the preselectingtype in that they automatically step off the terminals of a busy trunk and on to the terminals of an idle one a'ssoon as the test terminal of trunk to which ai trunk selector or several trunk selectors are "connected through their respective brushes,

is made to test busy by the trunk being taken into use. Consequently, when ground is applied to conductor 322, the trunk, by virtue of its having been taken into use at the posii tion where key 300 was depressed and relay 301 of the position circuit operated, relay 311 of some other position whose trunk selector is standing on theas signed trunk, 15 caused to operate since conductor 322 is multipled to z the corresponding terminals of the arcs of the other trunk selectors of the same trunk group. The ground on this conductor will close a clrcuit to relay 311 of this other position by way p of the bottom back contacts of the associated .3 relay 301 at that position, interrupter contact of trunk selector magnet 329, winding of relay 311 to battery on the bottom'lower contacts of rela 31.2. Bela 311 of the other position, on operating, connects ground from the bottom inner back contacts of relay 306,.

its own front contacts, to the winding ofthe selector magnet 329 causing it tooperate.

When the selector magnet breaksits inter rupter contacts relay 311 releases,in turn 5; opening the circuit ofthe selector magnet 329. The selector switch then advances to the next set of trunk terminals and if the trunk connected thereto is idle there is-no ground on the test conductor of the trunk corresponding to conductor 322 but battery through the winding of relay 216 of the idle trunk will be connected there instead, and relay 311'will, accordingly, not operate. The selector, therefore will remain on theterminals ofthe idle us trunk. On the other hand,rif tlie'succeeding trunk to which the trunk selector has been advanced is also busy, ground is connected to the test conductor thereof, relay 311 will operate again over the path previously described and the operating circuit forthe selector magnet 329 is closed again to advance the selector brushes to the terminals of the next idle trunk.

Should the case be that several trunk selectors are standing on the terminals of the same idle trunk at the time when an operator de-' presses key 300, the ground connected to conductor 322 will operate the respective relays 311 in those other trunk group position cir cuits whose trunk selector brushes are con nected to the terminals of the same trunk and cause each of the selectors to step off the busy trunk in themanner already described. The selector brushes of each trunk group position circuit, therefore, normally stand on the terminals connected to conductors 326, 322, 327 and 328 of an idle trunk. As already shown, any number of trunk group position selectors up to and including the total number of selectors may be standing on terminals associated with the same idle trunk and all but the one associated with the position where key 300 is depressed will step off the terminals of the trunk when the trunk is taken into use at the position by the depression of the said key.

Should it happen that, at the time the operator depresses key 300, all of the trunks leading to the community oflice are busy, lamp 313 at the position where the key is depressed is lighted as an indication of this fact, the trunk group busy register 325 is operated and the trunk selectors are prevented from any further hunting for idle trunks. This'is accomplished as follows: Relay 305 is normally held in an operated position from ground on conductor 323 which is multipled to the back contacts of all relays 216 of'the trunk group. When these relays are normal, indicating that their respective trunks are idle, this ground serves to maintain relay 305 operated and which, in turn, maintains relay 324 operated over an obvious circuit. So long as there is one trunk idle, there will be a ground on conductor 323. When the last idle trunk is taken into use and its associatedrelay 216 operates as described, the last multipled ground is removed from conductor 323 and relay 305 releases. Relay 305, when released, closes ground on its back contacts to operate relay 306. The release of relay 305 also releases relay 32 1 and when relay 324 makes its back contacts the trunk group busy register 325 operates its counting mechanism to register an all trunks busy con- 1 dition. The operation of relay 306 removes, at its back contacts, the grounds leading to the front contacts of relays 311 in the various trunk groups so that, when the last trunk of the group becomes busy, all the trunk sewinding of relay 310 and winding 302 in series a to ground on conductor 331 to the contacts of key 300. However, since relay 302 is marginal, it will not operate in series with high resistance relay 310. Relay 310 however, does operate'and connects ground from the top inner front contacts of relay 306, front contacts of relay 310 to lamp 313 at the position thereby lighting this lamp as an indication to the operator that no trunk to the community dial office is available. '1 he conductor connecting to lamp 313 is multipled to other trunk selector circuits in the same operators position, should there be two or more of said circuits serving different community dial offices. In such cases, lamp 313 functions to indicate an all trunk busy condition for the particular trunk group whose associated key is operated. It is seen, therefore, that when all trunks in the group are busy, the preselecting feature is stopped, since notrunk I is available to preselect1on, wh1le lamp 313 is lighted at the position where key300 was depressed to indicate the vabsence oflan idle trunk and the message register 325 operated to register an alltrunk busy condition In case key 300. is depressed while the as sociated trunk selector 329 at the position is hunting for an idle trunk, relay 301 will not operate since no battery is present on conductor 322 at the time, as it isassumed that the trunk selector is testing a busy trunk at the instant the operator depresses the key. The failure of relay 301 to operate prevents interference with any existing .dial connections at other positions. Relays 310 and302, however, will function in the manner described but lamp 313 will not be lighted due to the fact that, since all trunks are not busy,

relay 305 is operated, relay 306 released, and

there is no ground available on'the contacts of relay 310 with which to'close the circuit of lamp 313. If key 300 is still depressed when the selector brushes reach the terminals of an idle trunk circuit, relay 301 will operate, short-circuiting and releasing relay 310 by battery on its top left front contacts, open the path of relay 311 at its lower contact to prevent further operation of trunk selector and thereby causing it to stop on the terminals of the idle trunk. I g a Assuming that when key 300 is depressed a trunk is assigned at the position and trunk lamp 334 is lighted as an indication that the trunk has been assigned, the operator is ready to dial the number of the Wanted subscriber, as the position dial 315 is now connected in series with the pulsing circuit of theautomatic switches at the community dial ofiice over the trunk conductors already described.- I v p v W'heii the position dial 315 is moved oflnormal, contact 309 is opened and ground is removed from conductor 335 and hence from the bottom contacts of relay 304. As the dial restores to normal dial impulses are sent over the talking conductors and cause the auto- 327 and 328 as matic switches in the community dial office to 7 follow the impulses inthe well-known manner, These impulses are transmitted over the talkingconductors by way of conductors 332 and 333, thetop outer and middle contacts of relay 302 brushes 316 and 317 of the trunk selector 329, conductors 328 and 327, top'contacts of relay 218, conductors 229 and 228 of the trunk line extending to the stepbystep switches in, the community oflice and serve to operate these switches to reach the called subscribers line. The protective cir cuit composed of resistance 308 and condenser 307 bridged across conductors 332 and 333 is for the purpose ofproteeting the pulsing contacts of dial 315. 7

As mentioned p r,eviously,'no restriction isiniposed'on the .operator;as to thetime of inserting the calling trunk plugT into the .ja'clrC of theoutgoing trunk to the community dial office; She may insert it either be- .fore', during or after, dialing but before the depression of dial release key 321as described below. lWhen the'trunkplugT ispartially inserted into the jack, relays 204 and 213 of the outgoing trunk operate in series with relay 116 of theinteroifice trunk-over the following circuit {Battery on the winding of relay 116,'wi1iding of relay 116, sleeve conductors 121 and'236, winding of relay 204, winding of relay 213. to ground. The operation of relay 204 connects ground on its front contacts to conductor 322 which performs no useful function at this time. Relay 213 connects' ground on its front contacts to a common ground'conductor which connects to'the locking contacts of relay 221, thewinding of relay-214, thelocking contacts of relay 215, the, locking contacts of relay 206 and the winding of relay 209 through the top outer back contacts of relay 206 and to lockingcontacts of relay 203. Relay 209 operates. Re-

lay 116 of the interoifice trunkalso operates,

over the above tracedcircuit, closes through its top outer front contacts the tip talking conductor 144 to the tip conductor 123 of the trunk disconnects battery from relay [115 which releases, operates relay 110 from 1 ground on its top inner front contacts and preparesacircuit, on its bottom front contact's to operate relay 126whe'n the called subscriber answers as more fully described hereinafter. The operation of relay 110 removes battery from relay 109 which relay, however being slow to release, holds over its locking contacts to battery on the bottom outer front contacts of relay 110. Relay 110 also-disconnects conductor 118 and therewith disconnects battery through interrupter 156 from lamp 111 and replaces it with steady battery over the top inner back contacts of relay 126 and top front contacts of relay 110 for lighting this lamp as a ringing signal..

WVhen the trunk plug T is fully inserted into the trunk jack, relay 208" is bridged across the talking conductors 230 and 231 at the top and bottom inner back contacts of relay 206. If the interofiice trunk shown in Fig. 1-A were equipped with machine ringing in the known manner, relay 208 would immediately operate from the ringing current circuit in the trunk. It is necessary, in a connection to a community dial oflice equipped with well-known step-bystep apparatus to disconnect the ringing current circuit, normally a component part of such a trunk, when it is used to extend an incoming call directly to a wantedsubscribers line therein, since the step-by-step switches located therein have their own 10- cal ringing current supply which is used to bring the community dial office subscribers line. In the embodiment of the invent1on here disclosed, the ringing circuit is con-- trolled through key 130 and the operator may or may not depress the ringing key 130 before she has depressed the dial release key 321 as she chooses. Should she operate ringing key 130, however, before operating key 321, relay 208 operates over the ringing currentcircuit closed by the operated contacts of key 130. With the operation of relay 208 a path is closed to operate relay 207 from ground on the contacts of relay 209, contacts of relay 208, winding of relay 207 to battery. Relay 207 operated, looks over its top outer front contactsto the operating ground on the contacts of relay 209, operates relay 206 from ground over its bottom outer front contacts and connects grounded resistance 224 and battery through resistance 225 to the talking conductors 230 and231, respectively. Relay 206 opens the circuit of relay 209 at its top outer back contacts and looks over its outer bottom front contactsto ground on the front contacts of relay 213. The ringing circuit in the interoflice trunk is now tripped inthe well-known manner by the operation of a trip relay in the ringing circuit in series with the ringing current circuit and through a series path either to resistance 224 to ground or resistance 225 to battery. Relay 209 releases after a time interval and, in

turn, releases relay 207. The release of relay 207 disconnects ground supplied through resistance 224 to conductor 230 and battery supplied through resistance .225 to conductor masses 281 and connects, through its top and hot tominner back contacts, conductors 230 and 231 respectively through to the windings of retard coil 210. Relay 209 is made slow to release in order that resistances 224 and 225 tion to a community dial ofiice, is not necessary. The circuit can be revised to omit this feature if so desired. In the case of interofiice trunks arranged for automatic machine ringing the means described above are necessary since the ringing circuit is connected to the line without the operation of a ringing key. In order to make the traffic routine consistent, however, it is desirable to include the ringing feature so that an operator in using similar trunks on difierent types of connectors would be governed by the same traffic routine.

When the ring conductor 122 of the interofiice trunk is connected with the ring con-V ductor 231 of the outgoing trunk, and when relay 207 has been released as already described, relay 214 operates over a circuit traced from battery in the interoflice trunk I repeating coil winding 125, winding of relay 129, bottom normal contacts of ringing key 130, ring conductors 122 and 231,

bottom inner front contacts of relay 206, bottom inner back contacts of relay 207, top back contacts of relay 215, winding of relay 214 to ground on the front contacts of relay 213. Relay 214 operates causing relay 215 to be operated over an obvious circuit and relay 212 to be operated over the top back contacts of relay 211. Relay 215 operated, looks over its top front contacts to ground on the front contacts of relay 213 and, at the same time, extends this ground to the winding of relay'212 over its operating path as previously described and opens, at its top back contacts, the operating circuit of relay 214 thereby causing this relay to release. Relay 214 is, therefore, disconnected from conductor 231 at the top back contacts of relay 215. Relay 212 operated, closes a circuit on its front contacts to connect a holding bridge consisting of the windings of retard coil 220 and relay 219 across the talking conductors 228 and 229 extending to the community dial office selector switches when The above described dependence of the holding bridge across the trunk to the comniunitydial o'llice on the successful closure of the ring of the interoflice trunk plug with the ring contact of the outgoing trunk jack'is made in order to avoid signalling the called "subscribe in the community dial office unless the trunk plug has-been fully inserted into the outgoing trunk ack andboth talkingconductors has joined, which assurance is provided by the well-known mechanical structure of the trunk plug and ack wherein the successful contacting of the ring of the plug with the ring contact of the jack assures equally successful contacting between the tip of the trunk plug and the tip contact of the jack. In case the trunk plug'hasnot been fully inserted, relays 21l andj215- do not operate, a holding bridge is not provided andthe connection will be broken down as soon as key 321 is operated, due to the lack of the said holding bridge across the talking conductors to the community 'dial olflce after the loop over these conductors formed through the contacts of position dial 315 is opened by'the release of key 321 as described hereinafter. If the trunk plug is fully inserted the removal of this short-circuit permits a current flow to be established over a circuit in series with the automatic equipment at the community dial oilice connected to conductors 228 and 229 through the winding'of relay 219 and retardation coil 220. The current flowing through this circuit at this'time is in such a direction as not to operate relay 219.

pulses, which are transmitted over the parallel' loop formed by conductors 228, 229, 328, 327. 333 and 332. r lVhen the complete number has been dialed and the interolfice trunk plug has be'eninserted into the out oing trunk jack as already described, key 321 is operated, thereby causing the operation of relay 304 by connecting ground to conductor 336. Relay 394 locks to ground on the low-er frontcontacts of relay 302 over its own top contacts and the bottom contacts of relay 303. At its jbottom con- 335, to the Winding of relay 312. lVhen the dial restores to normal, with key 321 operated, relay 312 operatesover a circuit from ground on contacts 309, conductor 335, botated contact causing relay 22lr elay 219 in 826 by Way of selector brush 319 and associto operate and lock to ground over its own bottom front contacts,disconnects battery at its bottom back contacts from the winding of relay 311 aud'operates relay 303 by ground on its top front contacts. Relay 303 removes locking ground forrelays302 and 301 its top contacts thereby causingthese' relays to release and, at its bottom contacts, unlocks relay 304- which also releases. The release of relay 302 disconnects conductors 32? and 328 from the position .dial3l5 overpconductors 332 and 333ydisconnects operating batteryfrom relay 312 and battery to conductor are of the circuit of the trunk lamp 334, thus extinguishing it. .Relay 301 released, disconnects oper ating battery-from the Winding of relay 302 and connects aground supplied from relay 221 over conductor 322 to the Windingof relay 311 by \vay of conductor 322,;selector brush 318 and associated contact, the bottom back contacts of relay 301 and lnterrupter contacts of-selectonmagnet 329. The release of relay d releases relay 312.. a Relay -31-2 released, disconnects ground from its top front contacts to conductor 32-3, releases relay303 and opera -ela-y311 by bat tom bacirc over a path previously tracedand the selector that ground vvill beconnected to, conductor 326 for a length of time suliicient to properly operate relaysin the trunk circuit as more, particularly described hereinai ter.

Relay 303isalso'madeslow to operate for the additionalreason of insuring holding the selectors inthe distant community dial ofiice While transferring the talking conductors 228 and 229 from the position dial 315150 the holding bridge composed of-retardation coil 220 and the trunk circuit as already described; 7 3 i Ground on conductor 3 26 operates relay 221' in the trunk circuit as already describedwhich, in turn, connects direct ground from its top inner front contacts to conductor 322to replacetlie busy ground removed theretacts, relay 304 connects the ground IOm the from by the release of relay Relay 221 normal contacts 309, of the dial 315, conductor 228 and 229 towards the interolflce trunk cir cult." Relay 221-also operates relay 217 over an obvious circuit and this relay, in turn, op-

crates relay 218 also over an obvious ci .nit.

Relay 218 disconnects, at its top back contacts, the conductors327 and 328 from the talking conductors 22 9 and 228, respectively,

connects another ground-'- i-from' its bottom on its botlitacts to ground on conduct0l1322, over a path already. described. lhej opera-- tion of relay 3ll operatesselector magnet 329 inner front contacts to conductor 322. and opens itsv bottom back contacts which connect with the top front contacts of relay 203.

If key 321 is operated before the plug of the interofiice trunk is inserted into the outgoing trunk jack, the operation of key 321 connects ground to conductor 336 ultimately resulting in operating relays 221, 217 and 218 as already described. WVhen relay 221 operates, however, the switches in the community dial oiiice will be released due to the fact that relay 212 is not operated and therefore no holding bridge is placed across the talking conductors 228 and 229. The operation of relay 218 connects direct ground to'conductor 322 as already described. Vhen key 321 is released, the selector magnet 329 is operated over the circuit previously described and causes it to step 011 the terminals of the trunk. Ground is thereby removed from the conductor 326 thereby releasing relays 221, 218 and 21'? in turn disconnecting ground from conductor322, releasing relay 216 and restoring the circuit to normal. Relays 221, 218 and 217 are made slow to release to insure that ground on conductor 322 will remain connected thereto for a length of time suflicient to operate the selector magnet 329 and prevent the preselection of the trunk circuit before the automatic switches in the community dial oflice have restored to normal.

\ The called subscriber is signalled by the ringing current circuit of the automatic switches at the community dial office andv when the receiver is removed from the switchhook the circuits in the community dial oflice function to reverse the currentthrough relay 219 and retardation coil 220, and to thereby operate relay 219. Relay 219, on closing its front contacts, connects resistance 226 in series with the retardation coil 210 which, by the closure of the contacts on relay 219 closes a loop across the talking conductors 230 and 231. This circuit extends from battery on the winding 125 of the interoffice trunk repeating coil winding of relay 129, ring conductors 143,122 and 231, bottom inner front contacts of relay 206, bottom inner back contacts of relay 207, one winding of retarda-' tion coil 210, front contacts of relay 219,-resistance 226, bottom outer back contacts of relay 211, other Winding of retardation coil 210, top inner back contacts of relay 207, top inner front contacts of relay 206, tip conductors 230, 123, 144, repeating coil winding 12 1, to ground, operating supervisory relay 129 in the interofiice trunk circuit.

The operation of relay 129 when the called subscriber removes his receiver from the hook, operates relay 126 over a circuit from battery on bottom front contacts. of relay 116, winding of relay 126, bottom normally made continuity contact-s of relay 126, front contacts of relay 129 to ground on inner bottom back contacts of relay 126. Relay 126 short-circuits the bottom high resistance winding of relay 106 through its top front contacts and causes thereby a greater flow of current over the talking conductors 127 and 128 and, the cord supervisory circuit connected thereto. This increase of current flow operates the supervisory relay 105 of the A cord in the well-known manner and extinguishes lamp 131, thereby indicating to the A operator at the originating oflice that the called subscriber has answered. Relay 126 looks to groundon its own bottom outer front contacts. Relay 126 also extinguishes lamp 111 by opening its circuit at its top inner back contacts as an indication to the B operator that the called subscriber has answered.

In case the called subscribers line is busy at the community dial oflice current reversals at suitable intervals are sent back over the talking conductors from the community dial office in the Well-known manner. Relay 219 follows, these reversals, in turn causing the supervisory .relay 129 in the interoiiice trunk circuit to flash, which on its first operation, operates relay 126 as already described, and this relay, in cooperation with relay 129 alternately short circuits the high resistance winding of relay 106 which effects the supervisory relay 105 in the A cord and causes it to intermittently operate and flash lamp 131 also, resulting in an indication to the A operator that the line is busy. At the same time a tone is supplied from the community office and is transmitted back over the talking conductors and condensers 145 and 1416 to the calling subscribers stat-ion in the well-known manner to indicate to him that the called line is busy.

WVhen the receiver is replaced on the switchhook in the community dialofiice battery is reversed over the talking conductors 228 and 229 causing the release of relay 219. The release of relay 219 removes, at its front contacts, the bridge consisting of retard coil 210, and resistance 226 in series from across the talking conductors 230 and 231 on the incoming side of the trunk. Relay 129 thereby releases which, in turn, opens the short-circuit around the high resistance Winding of relay 106. The decrease in current in the trunk conductors releases the supervisory relay 105 in the A cord circuit and causes the supervisory lamp 131 to burn steadily in the wellknown manner as an indication that the called subscriber has restored. \Vhen the calling subscriber restores, lamp 132 in the A cord circuit is caused to light in the well known manner by the release of relay 15 1. The removal of the A cord plug P from the trunk jack J releases relay 106. Relay 106, in turn, releases relay 109. Relay 109 now supplies battery from the front contacts of relay 110 through its bottom back contacts, resistance 147, and lights lamp 119 as a disconnect sigtion between a calling subscriber in thesame ofice in which the community dial oiiice ter-.

minates, the same trunk can be used and the connection is established at the dial A position to which the said trunk is multipled. (e will 110W proceed to describe such a connection in which Figure 1B shows the connecting circuits at the dial A position.

When a calling subscriber signals the A operator, she obtainsfrom him the number of the wanted subscriber in the well-known manner. She proceeds thereafter to manually select an idle. trunk extending to the comn'iunity dial ofiice by the well-known method of testing the sleeve of the outgoing trunk jack with the tip 102 of the A cord. if the trunk'is busy because of aconnection set up at a B position relay 205 is operated as already, described and a battery potential is present on the sleeve conductor 233 from the inner front contacts of relay 205 thereby causing the trunk to test busy. The absence of battery potential then, indicates the idle condition of the trunk and the cord plug M is inserted into outgoing trunk jack D at the A board; If the trunk is idle relay 205 is normal and conductor 233 is connected through the bottom inner back contact of relay 205 to the winding of relay 202 which relay is also connected in series withthe winding of relay 21.3. The insertion of the cord plug M into the outgoing trunk jack D causes the operation of relays 202 and 213 in series from battery supplied over the sleeve conductor 100 of the A cord in the well-known manner, to ground on the winding of relay 213. Relay 202 causes the operation of relay 1 303 "from ground on the bottom backcontacts of relay 205, front contacts of relay 202 to the winding of relay 203. Relay 203, in turn, operates relay 221by connecting ground on its front outer top contacts to the winding of rela by way of the'bottom back contacts of relay 218 and, at the same time, extending this ground over another top outer contact to conductor 322 to make the trunk busy at the B position trunk selectors. Relay 216 is also operatedby this ground but performs no function other than to remove ground from conductor 323 for registering purposes as already described. When the plug of the cord circuit is fully inserted in the trunk jack, relay 214 operates from battery on J the A repeating coil winding 136, winding of relay- 148, normally made bottom contacts on ringing key 134, normally made bottom contacts of dial key135, ring conductors 137and119,

top inner back contacts'of relay 205, top nor-f mally made contact ofrelay 215, winding of relay214 toground on the front contacts of relay 213. Relay 214 operates relay 215 as alreadydescribed. ground on the front contacts of relay 213, and operates relay 212 as already described. The operation of'relay 212 closes a bridge composed of the windings of retardcoil 220 in series with relay 219' across the'ta'lking' conductors 228 and 229 to the community dial oihce,-causing the switches in that office to prepare for dialpulses. The talking condoctors 120 andl19 are associated withthe subscriberoperators positiondial 150 by the Relay 215 locks 'to' operation of key 135 in; the cord circuit.

Moving the position dial ofi' normal to dial the first, digit operates relay 200 over a cir cuitfroi'n ground on the off normal contacts 140 of dial 150,'bottom make contacts ofkey- 135, ring conductors 137 and- 119, top inner back contacts of 205, onewinding of retard coil210, back contacts of relay 219, lower front contacts of relay 215, lower front contacts of relay 203, winding -ofrelay 200 to battery. The operation of relay-200-operat'es relays 201 and 211 in parallel over an obvious circuit. Relay 211 operated disconnectsthe talking conductors 228 and 229 extending to the community dial office from the condensers 23 1 and 235 respectively, connects the extension of conductor 120 over the top outer front contacts of relay 211 to the winding ofrelay 212, and, at its lower inner iront contacts short-circuits the'bridge composed of the retardcoil 220 and relay 219, thus providing a direct loop from conductor 228 to conductor 229 of the trunk to" the community dial oflice through the contacts of relay 212. Relay 201 operated provides an additionalshort-circuit for the bridge composedof the windings of retard coil 220 and relay 219. p 5

Relay 212 is thus connected to ground in the pulsing contacts of dial 150 throughthe tip conductors 120 and 102, top tacts of key 135, contacts 151 of dial 15 0, while its contact is looped across'conductors make con- 228 and 229 so as to furnish'opencircuitimreoperates on these impulses and transmits, in turn, open circuit pulses over-tlietalki11g conductors 228 and 229 to control the switches in the community dialoiiice. VVhen the dial has restored to normal the circuitofrelay200 is opened at, dial contacts 140. Relay 201 is made slow to release a'nd will not release be tween the dialing of successive digits." .When" the completeinumber has been'dialed ,'relay 200 releasesand causes relay 201 tostart to release. Relay 200 also releases 211. The release of relay '21'1 reconnects the talking conductors 22 8 and 229 to the community ofiice through condensers 234 and 235, transfers the holding path for relay 212 from conductor 120 back to ground on the contacts of relays 213 and 215, reconnects condenser 232 and resistance 226 to conductor 120 and disconnects the short-circuit around the bridge composed of relay 219 and retard coil 220. This bridge however remains short-circuited by the contacts of relay 201 until this relay releases. Relay'201 is made slow to release so as to maintainthe short-circuit sufficiently long to allowthe automatic switch pulsing relay sufficient time to operate before placing it in series with the high impedance bridge of retardation coil220 and relay 219. Otherwise the. slow reoperation of the pulsing relay in the switches in the community ofiice would result in the pulse relay contacts remaining open on the final pulse for a length of time which might be sufficient to cause the switch i scribed for the connection set up at the position; V

in the community dial otfice to be released and thus cause the connection to be lost.

The operation of the ringing circuit as well as the various switchboard signals when the 'ca'lledsubscriber answers, or is busy or does not answeris the same as previously de- What is claimedis: 1. In a telephone system, a main oilice, a switchboard position equipped with a dial in said main office, an automatic satellite ofiice connected by trunk lines to said main office, saidtrunk lines terminating at said switchboard position, a key at said switchboard position designating said satellite office, a

switchboard position equipped with a dial at' said main otfice, a selector. switch in said switchboard position, an automatic satellite office connected by trunk lines to said main oflice, said trunk lines terminating at said switchboard position and multipled to terminals of said selector switch, a key at said switchboard position designating said satel-.

lite oiiice, means for stepping said selector switch off respectiveterminals of each oi saidtrunks; when busy, a relay operatively 'res ponsive to operation of said key, and

'means foroperatively associating said position dial-through contacts of said operated relay with the idle trunk on which said selector switch is standing at the time said key is operated. V r V V 3. Ina telephone system, a main ofiice, a switchboard position equipped'with a dial at said main oiiice, a selector switch in said switchboard position, an automatic satellite ofiice connected by trunk lines to said main oiiice, said trunk lines terminating at said switchboard position and multipled to terminals ofsaid selector switch, a key .at said switchboard position designating said satellite office, a dial release key at said switchboard position, means for stepping said selector switch off respective terminals of each of said trunks when busy, a relay operative responsive to the operation of said first key for operatively associating said position dial with the idle trunk on which said switch is standing, and means controlled by said dial each of said switchboard positions and'also multipled to terminals of each of said selector 7 switches, a lamp at each of said switchboard position-s for each of said trunks multipled thereat, a key at each of said switchboard positions designating said satellite oflice, a relay in each of said switchboard positions operative responsive to the operation of said key, means for stepping said selector switch oii respective terminals of each of said trunks when busy, and means for lighting the lamp of the trunk on which said selector switch is standingthrough contacts of said operated relay at that one of said switchboard positions where said key is operated.

5. In a telephone system, a main office, a switchboard position at said main oilice, a

selector switch in said switchboard position,

an automatic satellite office connected by trunk lines to said main oilice, said trunk lines terminating at said switchboard position and multipled to terminals of said selector switch,

a lamp at said switchboard position, a key at said switchboard position designating said satellite office, a relay operatively responsive to operation of said key, means for stepping said selector switch oil respective terminals of each of said trunks when busy, means for stopping further operation of said selector switch when all trunks are busy, and means controlled through contacts of said operated relay for lighting said lamp when all trunks are busy at the time said key is operated.

6. In a telephone system, a calling line, a switchboard position equipped with a dial, an automatic community oilice a trunk having a holding and signaling; bridge, said trunk extending from said switchboard position to said community oifice, a'key in said switchboard position designatingsaid community ofiice, a dial release key in said switchboard position, means for assigning 1 said trunk to saidswitchboard position when said key designating said community officeis operated, a cord circuit forinterconnecting said calling line with said trunk, means for associating said position dial withsaid assigned trunk when said key is operated, and means responsive to the connect-ion of said cord circuit with said trunk for connecting said holding and signaling bridge across conductors of said trunk after said dial release key is operated.

7. In a telephone system, a first times, a calling line in said first office, a second oilice,

munity oflice is operated, a second trunk for interconnecting said calling line in said first ofiice with said assignedlfirst trunk, means for associating said position dial with said assigned first trunk when said key is operated, means for disconnecting said dial from said assigned first trunk when said dial release key is operated, and means responsive to the connection of said second trunk with said first trunk for connecting said holding and signaling bridge across conductors of said first trunk after said dial release key is operated. a

8. In a telephone system, a firstjofiice, a calling line in said first ofiice, a second office, a switchboard position in said second ofiice, a community ofiice, a first trunk extending from said switchboard position in said second oflice to said community office, a key in said switchboard position designating said community oflice, means for assigning said first trunk to said switchboard position when said key is operated, a second trunk for interconnecting said calling line with said first trunk, a ring ing circuit, means for connecting said ringing circuit to said second trunk, means in said first trunk responsive to the connection of said second trunk with said first trunk'for extending said ringing circuit to said first trunk, and means in said first trunk responsive to said ringing circuit for disconnecting said ringing circuit from said first and second trunks respectively. p

9. In a telephone system, a'fii'st ofiice, a calling line in said first oifice, a second o'fiice, a switchboard position equipped-with adial in said second ofiice, an automatic community ofiice, a first trunk extending from said switchboard position to said community office, a keyin said switchboard position designating said community office, a dial release keyat said'switchboard position, means for L assigning said first trunk to said switchboard position when said key designating said community oflice is operated, a second trunk ior interconnecting said calling line in said first oifice with said assigned first trunk, a ringing circuit, means for connecting said ringing circuit to said second trunk, means in said first trunk responsive to the connection of said second-trunk with said first trunk for ext-ending said ringing circuit to said first trunk, and

.mea-ns-in said first trunkresponsive tosaid ringing circuit for disconnect ng said ringing circuit from said first and second trunks respectively. a v i 10. In a telephone system, awcalling line, a switchboard position equipped with a dial, an automatic community ofiice, a trunkline extendingfrom said switchboard position to said automatic community ofiice, a key in said switchboard position designating said, community ofiice, a dial release key at said switchboard po-sition, means for assigning said i trunk to said switchboard position when saidkey designating said community ofiice is op erated, a cord circuit for interconnecting said calling line with said trunk, a ringing circuit, means for connecting said ringing circuit to said cord circuit, means in said trunk responsive to the connection of said cordcircuit with said trunk for extending said ring-' 'ing circuit to said trunk, and means in said trunk responsive to said ringing circuit for disconnecting said ringing circuit from: said cord circuit and said trunk respectively.

11. In a telephone system, a switchboard position, a selector switch in said switchboard position, trunk lines, an automatic COITllllllnl ty oflice connected by said trunk lines to said switchboard position, said trunk lines terminating at said switchboard positionandmul tipled to terminals of said selectorswitch, a registering device, means for stepping said selector switch ofi respective terminals of each ofsaid trunks when busy, means for stopping further operation of said selector switch when'all of the said trunks are busy, and meansfor operatingsaid registering de vice when all trunks are busy. lQQIn atelephone system, a plurality of switchboard positions each equipped with a dial, a selector switch in each of said positions, an automatic community ofiice, automatic switches in said community ofiice, trunklin es extending from said switchboard positions tosaid'community ofiice, said trunk lines terminating in manual connection terminals at each of said switchboard positions designating. said community ofiice, a dial release key in" each ofsaid switchboard positions, means responsiveto the operation of said key at one of said; switchboard positions for assigning one its iio

its

disconnecting said dial from said assigned trunk when said release key is operated and means'for keeping said trunk line busy until,

said automatic switches in said communityoflice have restored to normal.

13.. In a telephone system, a calling line, a

switchboard position equipped with a dial, an automatic community oiiice, trunk extending from said switchboard position to said community office, a key in said switchboard posit-ion designating said community liice, means for assigning said trunk to said switchboard. position when said key is operated, a dial release key, a relay operatively responsive to the operation of said key and means controlled by said relay for disconnectingsaid dial from said trunk when-said release'key is operated and said dial is normal.- I V 14; In a telephone system, a calling line, an operators position equipped with a dial, an automatic community office, a trunk extending from said switchboard position to said community olfice, means for connecting said calling line to said trunk, a key in said switchboard position designating said community office, means in said switchboard position for associating said dial with said trunk and means responsive to the operation of said key for operating said means to operatively associate said dial with said trunk,

15. In atelephone system, a calling line,

an operators position equipped with a dial, an automatic community office, a called line in said community oflice, a trunk extending i fromsaid switchboard position to said community oifice, means for connectlng said callmg line to saldtrunk, means controlled by the operator for operatively associating said dial with said trunk, automatic switches in said community oiiice responsive to said dial for extending said trunk circuit to said called line, and meanscontrolled by the operator for operatively disassociating said dial from ofiice, a dial release key, means for connectingsaid callingline to said trunk, means" responsive toloperation of'said key for 0peraever associating said dial with said trunk, and means responsive to operation of said dialrelease key to operatively disa ssociate said dial from said trunk and to prevent their operative reasseciation while said calling line remains connected with said trunk.

17.111 a telephone exchange system, a

calling'line, a'switchboard position, an automatic community oliice, automatic switches in said lcommunity O'iI'lCB fi trunk extending from saidswitchboard position to said automatic switches in said community ofiice, a cord circuit for interconnecting said calling line with said trunk, a dial, means for operatively' associating said dial with said cord circuit, a pulsing relay in said trunk, means for operativelyconnecting said pulsing relay to said dial-over one-conductor of said cord and one conductor of said trunk, and means controlled by said pulsing relay for opera-- tively controlling d automatic switches in said community oflice. I

In witness whereof I hereunto subscribe my namethis 28th day of April, 1930.

I LINDLEY A. KILLE. 

